The present invention is related to a USB (Universal Serial Bus) port shared control method and pertains, in particular, to a USB port shared control method making it possible to let a plurality of virtual machines jointly utilize a physical USB host controller with which a USB device is connected via a physical USB port installed in a physical machine, and to let a single virtual machine occupy and utilize a physical USB port.
Normally, in case a USB device is connected with a USB port, the connection state is reflected in the PORTSC register which displays or controls the state of the port in the register of the physical USB host controller. And then, the USB drive of the computer, observing the contents of this PORTSC register, starts control of the physical port.
Moreover, in order to let a virtual machine use the physical USB host controller installed in the physical machine, virtualization of the USB host controller in the virtual machine is necessary. The virtualization of a USB host controller in a virtual machine such as this is implemented by carrying out, by means of shared technology based on device virtualization, device emulation with respect to the physical USB host controller by means of a hypervisor configured inside the host computer carrying out the control generating a plurality of virtual machines inside the physical machine.
Further, as prior art pertaining to the sharing of I/O devices in a virtual machine, there is known the technology reported in JP-A-2006-855431 (corresponding to U.S. Patent Publication No. 2006/0064523) etc.